A fluorosulfonyl imide salt such as N-(fluorosulfonyl)-N-(fluoroalkylsulfonyl)imide salt, di(fluorosulfonyl)imide, salt and derivatives thereof are useful as intermediates for compounds having a N(SO2F) group or an N(SO2F)2 group, and are also useful compounds in various applications, for example, electrolytes, additives for electrolytic solutions of fuel cells, selective electrophilic fluorinating agents, photo acid generators, thermal acid generators, and near infrared light-absorbing dyes. Particularly, since the fluorosulfonyl imide salt has high voltage endurance and conductivity, it is expected that various electrochemical devices having high performances can be obtained when the fluorosulfonyl imide salt is used as the electrolyte. Therefore, various studied have been made (Patent Documents 1 and 2).
Di(fluorosulfonyl)imides have conventionally been prepared by a halogen exchange reaction of chlorosulfonylimide using a fluorinating agent (Patent Documents 1 and 2, Non-patent Documents 1 and 2); by distilling fluorosulfonic acid (HFSO3) in the presence of urea (Patent Document 3).